//34. 在排序数组中查找元素的第一个和最后一个位置
class Solution {
    public int[] searchRange(int[] nums, int target) {
        int[] ret = new int[2];
        ret[0] = ret[1] = -1;
        //处理边界情况
        if(nums.length == 0){
            return ret;
        }

        //1.二分左端点
        int left = 0;
        int right = nums.length-1;
        while(left < right){
            int mid = left + (right - left) / 2;
            if(nums[mid] < target){
                left = mid + 1;
            }else{
                right = mid;
            }
        }

        //判断相遇的时候是否有结果
        if(nums[left] != target){
            return ret;
        }else{
            ret[0] = left;//此处返回left，right均可因为已经相遇
        }

        //2.二分右端点
        left = 0;
        right = nums.length-1;
        while(left < right){
            int mid = left + (right - left + 1) / 2;
            if(nums[mid] <= target){
                left = mid;
            }else{
                right = mid - 1;
            }    
        } 
        ret[1] = left;//此处返回left，right均可因为已经相遇
        return ret;
    }
}